Tractor transmission



Feb. 25, 1964 A. H. MARK ETAL 3,122,025

TRACTOR TRANSMISSION Filed March 29. 1961 3 Sl'lee'lZS-Sl'leel'l 1 lATTDRNEYS.

Feb. 25, 1964 A. H. MARK ETAL 3,122,025

TRACTOR TRANSMISSION Filed March 29, 1961 5 SheehS-Sheel'I 2 LN NINVENTORS. ALEXANDER H//VG MARK 8( Feb. 25, 1964 A. H. MARK ETAL3,122,025

TRACTOR TRANSMISSION Filed March 29, 1961 C5 Sheets-Sheet 3 INVENToRs.ALEXANDER H//VG MARK .Q

United States Patent O This invention relates generally to tractortransmissions and more particularly concerns an iniinitely variabletransmission suited for use in agricultural and industrial tractors.

rl`he primary aim or the invention is to provide an .ely variabletransmission wln'ch ailords the desired power characteristics fortractor Vuse and whose cornponents lit easily w in the spaceconventionally allotted to tractor transrni sions. indeed, it is anobject of the invention to provide a transmission of this type whichrequires no repositionin 7 of engine, PTO or output shafts whichutilizes the same transmission case normally employed for a standard,shiftable gear transmission.

lt is also an object to pro 'ide a transmission of the above characterwhich transmits substantial power with particularly good eici-ency thespeed ranges wherein tractors most reuently operate.

Another object is to provide a transmission as described above which isparticularly adaptable for economic l, efficient use in industrialtractors, agricultural tractors of .edium power, and modern horsepowertractors; despite the different demands each or such tractors make on atransmission.

Gtner obiects and advantages of the invention become apparent uponreading the following detailed description upon reference to thedrawings, in which:

l is a fragmentary elevation, partially in section, of a tractorembodying a transmission vctmstructed in accordance with the presentinvention;

FV". 2 is an enlarged longitudinal section of the transmisson shown inFlG l; and

FlG. 3 is a fragmentary section similar to FlG. 2, showing a modifiedform ot transmission also embodying the invention.

While invenbn will be described in connection with certain preterrerembodiments, it will be understood that we do not intend to limit theinvention to those ernbodi ents. Gn the contrary, we intend to cover allalternatives, modigcations and equivalents as may be included within thespirit and scope of the invention as de ned by the appended claims.

Turning now to PEG. l, there is shown a fragment oi tractor l@ whichincludes a transmission ll embodying invention. The transmi sion il isencased in a housthat is sandwiched between a motor case i3 and a erntial le. The transmission controls the application or power from anengine power shaft l5, vhich carries a usual llywheel i6, to atransmission output shart j] that drives differential gearing "adconnected to the rear axles i9 of the tractor, of only one is sh wn inthe drawings. The tractor it) includes rear drive wheels 2i? which aredriven with the axles i9 in the usual manner.

As is common, a power takeol or PTC shaft is journalled through thetransmission housing l?. and the ditierential housing ld so as topresent a splined power takeoff connection Ze at the rear of the tractorlb. The P'O shaft, at its forward end, carries a gear 27 which is inmeshing engagement with a pinion 2li that is directly coupled to theengine flywheel 16. The TO shaft 25 is thus constantly rotated wheneverthe engine of the tractor is driven and, thus, the tractor l@ isprovided with a live PT@ at the connection 2o. When not in use, theconnection 226 is shielded by a removable cover 29.

To provide a source of hydraulic fluid under pressure for the varioushydraulically operated mechanisms of the tractor it?, the shaft 25 isdirectly connected to a pump 3h mounted within the diiterential housingla. The PTC shaft 25 also carries a slntable gear 3l adapted to be movedinto rneslnng engagement w h a gear 32 secured to the transmissionoutput shalt i7. The arrangement may taire various forros either asshown Klemm 2,817,408, December 24, i957, or in lilies applicationSerial No. 550,9'l0 filed November 4, i959, now latent No. 3,041,884.When the shiitable gear 3l is moved into engagement with the gear 32,PTO shaft 25 is directly coupled to the dir'lererrtial gear'"g j: sothat the tractor it) is driven in synchronism with rotation of the PT()connection This mode or operation is useful when the tractor "iti isutilized with equipment that must operate at a fixed rate relative toits ground speed.

Lu accordance with the invention, an iniinitely variable pump-motordrive unit and the l'f shalt 25 are arranged to drive a com i nigplanetary 36 that is rotatably coupled to the transmission output shaftIl'. in the preferr-ed embodiment, the pump-motor d1 ive unit 353 is ofthe axially disposed, reciprocating piston type wmch includes axiallyalined pump and motor shafts 37 and 3S, respectively. The puro-p shaft37 is splined to a pump housing 39 in which are disposed a plura ity ofpump pistons d@ that are adapted to be axially reciprocated by atiltable wobble plate The motor shaft 3S is splined to a motor housingfil. having a plurality of axially shiftable pistons i3 which actagainst a fled bear ng plate to impart a torque to the motor shalt Thebearing plate 44 is carried by a drive unit housing that is anchored inplace between the edges of the bousings l2, i4. The housing d5 supportsa valve plate which is interposed between the pump and motor portions ofthe drive unit which is nrovided with the usual passages to control thetrans n of in order to serve as a control member for the drive unit 35,the wobble plate carries oppositeiy extending stub shaft portions Si)(see EEG. l) which are pivoted on the opposite side walls oi thetransmission housing l2. The tilted position ot the wobble plate iscontrolled by a hydraulic servo Si having an output plunger 52 connectedthrough a linl. 5:2 to an upstanding arm 55 on the wobble plate di. Aninput plunger 54 for the servo 5l is moved by a control lever 5S throughan Lerrnediate lever 56 that is pivoted on the drive unit housing Aswill be familiar to those skilled in the art, the output plunger ot theserv is hydraulically positioned with considerable force to correspondwith changes in the position o the input plunger 54. Thus, the operatorof the tractor itl, oy manipulating the lever controls the angle atwhich the wobble plate All is disposed and thus controls the speed atwhich the motor shaft is driven relative to the rotational speed of thepurnp shaft 37.

ln a drive unit of this type, the wobble plate normally has a range ofmovement of about 59 to 66 and is capable of being moved through a anglewith respect to the axis oi the pump shalt 37 so as to slow the torwarddriven speed 0i the motor shaft 3S to a non-rotating, locked-upcondition and tnen cause the motor shait 3S to be driven a reversedirection. Thus, the drive unit 3S permits the driven speed oi the motorshalt to be innitely varied relative to the speed of the pump shaft 37through a range from fast forward, in which the motor shaft 3S rotatesat least as rapidly as the pump shaft 37, to slow reverse, in which themotor shaft 3S is driven slowly in a reverse direction with respect torotation of the pump shaft 37.

The drive unit 35 also includes a control valve block 6% which regulatesthe hydraulic pressure between the pump pistons 4t and the motor pistons43. The wobble plate d1 carries a cam arm 61 (see FIG. 1) which, througha bell crank 62, adjusts the valving in the block 69. In addition, alever 63, operable from the left hand or opposite side of thetransmission case 12 as viewed in the drawings, operates a slide 6d toopen a hydrauli by-pass circuit in the valve block e@ which, in effect,relieves uid pressure in the drive unit 35 so as to esta`o lish afree-wheeling, neutral condition. Such arrangements are normal parts ofa pump-motor drive unit of which the unit 35 is typical.

Turning next to the combining planetary 36, the planetary includes a sungear 7@ which rotates as part of the motor shaft 3S, a ring gear 7ljournaled by bearings 72 on the drive unit housing d5, and a pluralityof planetary gears 74, of which only one is shown, joun naled on acarrier 75. rl`he ring gear 71 carries outwardly extending teeth 7lwhich mesh with a pinion 73 on the PTO shaft 25. The carrier 75 isrotatably mounted coaxially of the motor shaft 3S and extends to a pointadjacentthe transmission output shaft 17. ln the FIGS. 1 and 2embodiment, the carrier 75 is coupled to the output shaft 17 through aselectively operable reversing planetary 76 having the purpose andconstruction described in detail below. However, when the transmission11 is utilized in a standard, medium powered tractor, a direct couplingbetween the carrier 75 and the output shaft 17 can be employed so thatthese parts rotate as one. To facilitate a description of the operationof the drive unit 35 and the combining planetary 36, it will be assumedthat such a direct coupling has been substituted for the reversingplanetary 76 so that the carrier 75 directly drives the tractordifferential gearing 18.

With the tractor engine operated at its governed speed, the pump shaft37 is steadily driven in one direction through its direct coupling tothe engine shaft and the flywheel l5. The PTO shaft is steadily rotatedin the opposite direction through the pinion 23 and the gear 27. Theconstantly rotated PTO shaft 25 drives the ring gear 71 of the combiningplanetary 36 through the pinion 73 and the gear teeth 71. lt can thus beseen that the pump shaft 37 and the ring gear 71 rotate steadily in thesame direction so long as a tractor engine is operated.

When the drive unit is brought into operation by permitting a hydraulicpressure build-up between the pump pistons di? and the motor pistons 43,the motor shaft 33 and thus the sun gear 7i? of the combining planetaryare rotated. Tilting the wobble plate 41 to its extreme fast forwardposition causes the motor shaft 38 to be driven in the same direction,and at about the same speed, as the pump shaft 37. As a result, thecombining planetary carrier 75 is driven in the same direction as thering gear 71 and the sun gear 76 are rotated. Since we are assuming thatthe carrier 75 is directly coupled to the output shaft i7, the tractorlltl is then driven forward at its top speed.

The driving speed of the tractor is selected by the setting of thewobble plate 41. As the wobble plate is moved from its extreme tiltedposition toward a position at right angles to the axis of the pump shaft37, the motor shaft 33 and thus the sun gear 7b are driven at slower andslower speeds. As a result, the rotational speed of the carrier 75, andthe driving speed of the tractor, is reduced. When the wobble plate d1reaches at right angle position with respect to the axis of the pumpshaft 37, the drive unit 35 becomes locked up so that the sun gear 7b isnot rotated. However, the ring gear 71 continues to be powered from thePTO shaft 25 so that the planetary carrier 75 continues to be driven ina forward direction about the stationary sun gear 7).

As a feature of the invention, the gear ratios of the combiningplanetary 36 are preferably selected so that the carrier 75, and thusthe output shaft 17, when driven solely by the ring gear 71 propels thetractor 1@ at its normal working ground speed, which is usually in theneighborhood of about 6 mph. When so arranged, the tractor, workingnormally and under load at its usual ground speed, is driven solelythrough the PTO shaft 25 and the drive unit 35 remains locked up. Thus,there is no loss of eliciency through the pump unit 35 and all of theengine power is transmitted through positive mechanical couplings.

To drive the tractor in reverse, the wobble plate 41 is tilted through a90 angle with respect to the pump shaft 37 so that the motor shaft 58 isrotated in a reverse direction. This causes the sun gear 71B to rotatein a direction that is opposite to the ring gear 71 and, as the reverserotation of the sun gear 7b is increased upon further tilting movementof the wobble plate 41, the carrier 75 comes to a stop and then beginsreverse rotation.

When the transmission 11 is used in an otherwise standard tractor, andagain assuming a direct coupling between the carrier 75 and the outputshaft 17, a speed range of from +16 m.p.h. to -4 mph. is convenientlyobtained. As mentioned above, it is highly desirable to have the tractorreach its normal forward operating speed of about 6 mph. when the driveunit 55 is set in its locked up condition. The speed of the tractorwithin the full range is, of course, infinitely Variable upon propersetting of the wobble plate 41, through the servo 51, in response tomanipulation of the lever 55.

When a tractor is intended for industrial use, those skilled in the artwill appreciate that a full range of reverse speeds is highly desirableand to adapt the transmission 11 for this purpose is the function of thereversing planetary 7 6 mentioned above. The reversing planetary 76includes an input element in the form of a sun gear 77 formed, in theillustrated embodiment, as an integral portion of the combiningplanetary carrier 75. The output element of the reversing planetary 76is a carrier 78 that is keyed at 79 to the transmission output shaft 17.The carrier 78 supports a plurality of planet gears Si? arranged inpairs between the sun gear 77 and a ring gear S1 journaled by bearings82 in a housing bracket 83.

To establish a direct forward drive between the combining planetarycarrier 75 rand the transmission output shaft 17, an annular, fluidactuated, disk clutch e-f i activated to directly ycouple the sun gear77, and thus the carrier 75, yto the ring gear 81. This locks the sungear 77 and the ring gear 81 for simultaneous rotation and, of course,causes corresponding rotation of the output shaft 17 lin the samedirection and Iat the same rate as the combining planetary carrier 75.

To produce reverse rota-tion, the reversing planetary 75 includes ahydraulically actuated band clutch 25 which is clamped about the ringgear 81 to llock the ring gear relative to the housing bracket 33. Atthis time, of course, the disk clutch S4 is released. The sun gear 77then drives the double planetary gears against the stationary ring gearwith the result that the carrier 75 is rotated in a direction oppositeto the direction of rotation of the sun gear 77. In this way, rotationof Ithe output shaft l17 is reversed relative to the combining planetarycarrier 75 and thus a range of lreverse speeds substantially as great asthe range of forward speeds obtainable thro-ugh the transmission 1d isachieved.

To `adapt the Itransmission of the invention for use in high horsepowertractors where greater lspeed ranges can be efhciently utilized, themodification shown in FIG. 3 is particularly effective. of theinvention, parts corresponding to those previously described have been4given Ithe same reference numeral with the distinguishing sutlix aadded. Thus, the transmission 11a is enclosed in la housing 12a fittedadjacent to a rear or differential housing 14a. A combining planetary35a is driven from both a PTO shaft 25a and a pumpmotor drive unit 35aso as to power ya transmission output shaft 17a. The drive unit 35aincludes a housing 55a mounting a motor bearing plate 44a against whicha plu- In describing this modification Y up condition wherein the motorshaft is not rotated, said pump-shaft being alined with and coupled tosaid power shaft, a PTO shaft journalled in said housing parallel t saidpurnp andV motor shafts, said motor shaft and said PTO shaft beinggeared together for opposite rotation, a combining planetary including asun gear, ring gear and connecting planet gears journalled on a carrier,said sun gear rotating as part of said motor shaft, said ring gear beinggeared to and driven by said PTO shaft, and a transmission output shaftcoupled to and driven by said carrier, said planetary gear ratios beingselected so that said output shaft is driven at a slowV forward speedwhen said pump-motor is locked-up.

3. in a tractor transmission driven by a rotating power shaft, thecombination, comprising, a housing, an inhnitely variable pump-motordrive unit mounted in said housing and having oppositely extendingaxially alined pump and motor shafts, said pump-shaft being alined withand coupled to said power shaft, a PTO shaft spaced laterally of saiddrive unit and being journalled in said housing parallel to said pumpand motor shafts, said motor shaft and said PTO shaft being gearedtogether for opposite rotation, a combining planetary including a sungear, ring gear and connecting planet gears journalled on a carrier,said sun gear rotating as part of said motor shaft, said ring gear beinggeared to and driven by said PTO shaft, and a reversing planetarymounted on and driven by said carrier, a transmission output shaftmounted in said housing in alinement with said carrier, and means forselectively conditioning said reversing planetary so that said carrierrotates an output shaft in either forward or reverse directions.

4. In a tractor transmission driven by a rotating power shaft, thecombination comprising, a housing, a pumpmotor drive unit mounted insaid housing and having pump and motor shafts, said pump shaft beingcoupled to said power shaft, a PTO shaft journalled in said housing,said motor shaft and said PTO shaft being geared together, a combiningplanetary including a sun gear, ring gear and connecting planet gearsjournalled on a carrier, said sun gear rotating as part of said motorshaft, means for selectively coupling said ring gear for rotation withsaid PTO shaft, means for selectively locking said ring gear withrespect to said housing, a transmission output shaft, and a shiftablecoupling element for selectively coupling said output shaft directly tosaid motor shaft or to said carrier.

5. In `a tractor transmission driven by a rotating power shaft, thecombination comprising a housing, an infinitely variable pump-motordrive unit mounted in said housing and having ayially alined pump andmotor shafts, said pump shaft oeinfr alined with and coupled to saidpower shaft, a PTO shaft journalled in said housing pardlel to said pumpand motor shafts, Vsaid motor shaft and said PTO shaft being gearedtogether for opposite rotation, a combining planetary including a sungear, ring gear and connecting planet lgears journalled on a carrier,said sun gear rotating7 as part of said motor shaft, selectivelyoperable means for coupling said ring gear for rotation with said PTOshaft, selective-ly operable means for locking said 'ing gear withrespect to said housing, a transmission output shaft adiacent [to andalined with said motor shaft, and a shiftable coupling element forselectively coupling said output shaft directly to said motor shaft orto said carrier.

6. in la tractor transmission driven by a rotating power shaft, thecombination comprising `a housing, an infinitely variable pump-motordrive unit mounted in said housing and having axially al-incd pump andmotor shafts, said pump shaft being alined with and coupled to saidpower shaft, a PTO shaft jou-rna-lled in said housing parallel to saidpump and motor shafts, said motor shaft and said PTO shaft being gearedtogether for opposite rotation, a combining planetary including a sungear, ring gear and t.) connecting planet gears journalled on a carrier,said sun gear rotating yas, oart of said motor shaft, an annular duidclutch for cou ung said ring gear for rotation with said PTO shaft, aiselectively operable brake for locking said ring gea-r lwith respecttos-aid housing, a ytransmission output shalt adjacent to and alinedwith said motor shaft, and a shiftable coupling element for selectivelycoupling said output shaft directly to said motor ishaft or to saidcarrier, said element also having a neutral position in which saidoutput shaft is not driven.

7. ln a tractor having an engine driven power shaft and two paralleloutput shafts for traction drive and PTO drive respectiveh atransmission comprising, in combination, a continuously variable `andreversible drive unit Vhaving oppositely extending input and outputmembers, a differential gear assembly positioned adjacent said unit andhaving `three interacting polwer transmitting elements coupled togetherfor differential rotation, a PTO shaft journalled in alhiement with andbeing coupled to said output shaft for PTO drive, means coupling saidinput member and said PTO shaft for rotation with said power shaft, andmeans rotatably coupling one of said elements to said output member,another of said elements to said PTO shaft and the third of saidelements to said output shaft for traction dri-ve whereby IIlhe PTOshaft provides a power path paralleling said drive unit for both drivingthe output shaft for PTO drive and assisting the drive to the outputshaft for traction drive.

8. A drive system for a vehicle comprisin in combination, a driven powershaft, an output shaft, a continuously variable and reversible driveunit having input and output members with the input member beingdrivingly coupled to said power input shaft, a power transmitting shaftldrivingly coupled to said power input shaft, `a diff renti-al gearassembly connecting said drive unit '1nd lsaid power transmitting shaftto said output shaft so as to pro-vide a first drive path from saidinput shaift to said output shaft, means for selectively disconnectingsaid gear assembly from said output shaft and drivingly coupling saidoutput shaft to said output member so 'as to provide a second drive pathfrom said input shaft to said output shaft, whereby operation of saidmeans selects either of two drive paths both providing continuousvariability but with different speed and torque limits.

9. A drive system for a vehicle comprising, in combination, -a drivenpower input shaft, an output shaft, a continuously variable andreversible drive unit having input and output members with the inputmember being drivingly coupled to said power input shaft, a powertransmilt-ting shaft drivingly coupled to said power input shaft, adifferential Vgear assembly connecting said drive unit and said powertransmitting shaft to said output shaft so as to provide a first drivepath from said input shaft to said output shaft, means for selectivelydisconnecting said gear assembly from said output shaft and drivinglycoupling said output shaft to said output member so as to provide asecond drive path from said input shaft to said output shaft, and meansfor selectively disconnting said power transmitting shaft from said gearassembly and conditioning said gear assembly to drivingly connect saidoutput member to said output shaft so as to provide a third drive pathfrom said input shaft to said output shaft, whereby operation of saidtwo means selects either of three drive paths all providing continuousvariability but with dierent speed and torque limits.

References ited in the file of this patent UNITED STATES PATENTS2,599,814 Cull June l0, 1952 2,991,921 weydt sept. i, i959 2,901,922Baker Sept. l, i959 2,929,269 WO1/dt Mar, 22, 196,0

1. IN A TRACTOR TRANSMISSION DRIVEN BY A ROTATING POWER SHAFT, THECOMBINATION COMPRISING, A HOUSING, AN INFINITELY VARIABLE PUMP-MOTORDRIVE UNIT MOUNTED IN SAID HOUSING AND HAVING OPPOSITELY EXTENDING,AXIALLY ALINED PUMP AND MOTOR SHAFTS, SAID PUMP-SHAFT BEING ALINED WITHAND COUPLED TO SAID POWER SHAFT, A PTO SHAFT SPACED LATERALLY OF SAIDDRIVE UNIT AND BEING JOURNALLED IN SAID HOUSING PARALLEL TO SAID PUMPAND MOTOR SHAFTS, SAID MOTOR SHAFT AND SAID PTO SHAFT BEING GEAREDTOGETHER FOR OPPOSITE ROTATION, A COMBINING PLANET GEARS JOURNALLED ON ACARRIER, SAID SUN GEAR ROTATING AS PART OF SAID MOTOR SHAFT, SAID RINGGEAR BEING GEARED TO AND DRIVEN BY SAID PTO SHAFT, AND A TRANSMISSIONOUTPUT SHAFT COUPLED TO AND DRIVEN BY SAID CARRIER.